The invention relates to an apparatus for argon-plasma coagulation (APC).
High-frequency surgery, of which argon-plasma coagulation forms a subcategory, has been employed for many years in both human and veterinary medicine in order to coagulate and/or cut biological tissue. In this process, by means of suitable electrosurgical instruments high-frequency current is conducted through the tissue to be treated, so that this tissue is altered by protein coagulation and dehydration. Therefore a coagulation process can serve to close vessels and stop bleeding. A cutting process subsequent to the coagulation process then enables previously coagulated tissue to be completely separated from the remaining tissue.
Argon-plasma coagulation enables non-contact coagulation of tissue and serves for effective stanching of blood and devitalization of tissue. In this kind of coagulation an inert working gas, e.g. argon, is conducted through gas-supply devices from an argon-plasma-coagulation instrument, which determines the argon dosage and monitors for errors, to the tissue that is to be treated. The working gas can then be used to generate a plasma stream between a distal end of the gas-supply devices, e.g. a probe, and the tissue. The HF current can then be applied to the tissue to be treated without bringing the electrosurgical instrument into contact with the tissue. Hence the possibility of the tissue adhering to the instruments is avoided. The argon-plasma coagulation additionally prevents carbonization of the tissue as well as smoke formation and unpleasant odors.
The technique of argon-plasma coagulation can be employed both with an opened body and also by minimally invasive means. In the latter application the probe to supply the working gas is pushed into the body, e.g. through an endoscope, along a route through a natural body opening until it reaches the operation site in the relevant body cavity.
A disadvantage of known forms of APC apparatus and their probes resides in the fact that during insertion of the probe into the body cavity or after a probe has already been inserted, from a distal end of the probe it is possible for the working gas, as well as gases and/or liquids originating within the body, to flow back into the gas-supply devices. In this case the probe itself, but also elements of the apparatus for argon-plasma coagulation connected thereto, such as the APC instrument, become contaminated.
Therefore some of the known forms of apparatus provide sterile, hydrophobic membrane filters that are preferably positioned at a distal end of the gas-supply devices, i.e. in particular in the probe, and are intended to prevent reflux of gases and/or liquids. However, such filters are expensive, must be exchanged at regular intervals, and therefore require an enormous amount of maintenance and cost a great deal. Furthermore there is a risk of forgetting to exchange the filter, so that a subsequent operation will be carried out with a contaminated appliance. Once an appliance has been contaminated, it can no longer be reliably prepared for further use.
As an alternative, the known appliances provide for the working gas to flow continuously through the probe to the tissue to be treated. This likewise avoids backward flow. However, prolonged inflow for hygienic purposes floods the affected body cavity unnecessarily with the inert working gas, which can easily lead to complications during the operation. In addition, the whole APC apparatus must already be in operation when the probe is inserted, to ensure the flow of gas. And both appliance and gas flow must be switched on continuously, until the probe has been completely removed from the body cavity.